COLONIZATION AND REPRODUCTION OF THE EPIBIOTIC FLAGELLATE COLACIUM VESICULOSUM (EUGLENOPHYCEAE) ON DAPHNIA PULEX

The epibiotic flagellate Colacium vesiculosum Pringsheim attaches to planktonic species of Daphnia in freshwater habitats. Previous studies found that prevalence (percentage of substrate organisms carrying attached epibionts) and intensity (number of attached epibionts on a given substrate organism) are low early in the Daphnia intermolt period and are high late in the intermolt period. We tested the hypothesis that increases of Colacium cells attached to Daphnia occur both by rapid initial and continuous colonization and by cell reproduction. Epibiont prevalence and intensities were determined at successive intermolt stages of Daphnia pulex Leydig collected from freshwater ponds in Colorado. Colonization was continuous throughout the intermolt period and was most important to epibiont population increase at the beginning of the intermolt period. Cell division was the major contributor to epibiont increase at the end of the intermolt period.